274 Cc. M. JACKSON 
from 20 or 25 per cent of the gland at one week to 15 per cent 
at two weeks, 10 per cent at three weeks, and 7 per cent at ten 
weeks, increasing again slightly in the adult. 
2. The relative volumes of cortex and medulla are subject to 
considerable individual variation. Their ratio shows no distinct 
difference according to sex and is not materially changed in 
young rats stunted by underfeeding or in adults subjected to 
acute or chronic inanition. 
3. The vascular stroma (in comparison with parenchyma) nor- 
mally shows considerable individual variabilty in relative volume, 
due chiefly to the varying distention of the blood-vessels. In 
general, however, there is evidently an increased vascularity upon 
passing from the outer zone of the cortex (average 13 per cent) 
toward the medulla (average 28 per cent), with no constant 
change according to age. 
4. The changes in the volume of the vascular stroma during 
inanition are variable. In general, the stunted young rats show 
a marked hyperemia in the inner cortical zone, with relative 
anemia in the middle and outer ones; medulla unchanged. In 
stunted rats refed one to two weeks, the relative volume of the 
stroma in general returns toward normal, though the outer zone 
remains anemic. In adult rats with acute or chronic inanition 
the inner and middle cortical zones appear hyperemic, the medulla 
relatively anemic. 
5. With the exception of the first week, there is in general an 
increase in the size of the suprarenal parenchyma cells from birth 
to ten weeks of age, with little or no increase thereafter. The 
average change in cell diameter for the various zones between 
birth and maturity is as follows: outer zone, 7 » to 9 »; middle 
zone (outer portion), 9 u to 15 w; middle zone (inner portion), 9 u 
to 12 w; inner zone remains about 9 »; medulla, 8 » to 16 un. 
6. The nuclei increase slightly in diameter during postnatal 
life, excepting those of the inner cortical zone. The cytoplasmic 
increase is much greater, however, so the nuclei in general lag 
behind in relative size (nucleus-plasma ratio). Thus the relative 
nuclear volume decreases, in the outer cortical zone, from about 
44 per cent of the cell volume in the new-born to 23 per cent in 
